This invention relates to engine crankshaft machining for improving quality and fatigue life thereof and more particularly to new and improved work piece and back up roller constructions for deep rolling and strengthening the fillets of crank journals of crankshafts.
During deep rolling of the fillets defined by the annular undercuts of engine crankshaft journals, the fillet rollers experience high loads and mechanical wear from the back up rollers of the deep rolling machine. More particularly the back up roller imparts the large rolling loads directly onto the circumferential rolling edge of the fillet rollers as the crankshaft is turned in the machine and the fillet rollers impart deep compressive stresses in the fillets. The large loads directed onto small contact areas of the rolling edge of the fillet rollers by the back up roller effect fillet roller wear which materially reduces the service life of the fillet rollers and productivity of fillet rolling equipment.
This invention effectively increases the contact area between the back up roller and the workpiece or fillet roller so that the fillet roller loading is spread and fillet roller wear is resultantly reduced and tool life of the fillet roller is increased. More particularly by dividing the back up roller load so that it is directed to opposite sides of the annular working edge of the fillet roller, the rolling edge thereof experiences reduce wear so that fillet rollers, and deep rolling equipment life is increased. With this invention the rolling loads directed by the back up roller to the fillet rollers are on opposite sides of the rolling edge of the fillet roller so that fillet roller stability is improved during the deep rolling cycle.
This invention is particularly useful in increasing service life on a wide range of workpiece rollers and including those having a compound rolling radius to effect the optimized deep rolling of pin journals having undercuts with compound radii to increase the effective width of such journals.
It is accordingly a feature, object and advantage of this invention to increase the tool life of the work piece rollers of fillet rolling machines regardless of the undercut configuration. This invention provides a clear advantage over prior work piece rollers because of extended tool life resulting from the division and spreading of the rolling force over at least two discrete areas of the work piece roller and away from the rolling annular edge thereof.